Add DB indices to speed up purging rooms (#16457)

changelog.d/16457.bugfix

@@ -0,0 +1 @@
+Improve the performance of purging rooms, particularly encrypted rooms.

synapse/storage/databases/main/account_data.py

@@ -103,6 +103,13 @@ def __init__(
             "AccountDataAndTagsChangeCache", account_max
         )
 
+        self.db_pool.updates.register_background_index_update(
+            update_name="room_account_data_index_room_id",
+            index_name="room_account_data_room_id",
+            table="room_account_data",
+            columns=("room_id",),
+        )
+
         self.db_pool.updates.register_background_update_handler(
             "delete_account_data_for_deactivated_users",
             self._delete_account_data_for_deactivated_users,

synapse/storage/databases/main/e2e_room_keys.py

@@ -53,6 +53,13 @@ def __init__(
     ):
         super().__init__(database, db_conn, hs)
 
+        self.db_pool.updates.register_background_index_update(
+            update_name="e2e_room_keys_index_room_id",
+            index_name="e2e_room_keys_room_id",
+            table="e2e_room_keys",
+            columns=("room_id",),
+        )
+
         self.db_pool.updates.register_background_update_handler(
             "delete_e2e_backup_keys_for_deactivated_users",
             self._delete_e2e_backup_keys_for_deactivated_users,

synapse/storage/schema/main/delta/82/04_add_indices_for_purging_rooms.sql

@@ -0,0 +1,20 @@
+/* Copyright 2023 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+    (8204, 'e2e_room_keys_index_room_id', '{}');
+
+INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
+    (8204, 'room_account_data_index_room_id', '{}');